类的__dict__属性和类对象的__dict__属性
# -*- coding: utf-8 -*-
class TestDict(object):
a = 0
b = 1
def __init__(self):
self.a = 2
self.b = 3
def test(self):
print 'a normal func.'
@staticmethod
def static_test():
print 'a static func.'
@classmethod
def class_test(self):
print 'a class func.'
if __name__ == '__main__':
obj = TestDict()
print('class __dict__:', TestDict.__dict__)
print('class obj __dict__:', obj.__dict__)
输出结果
- 类的
__dict__:
('class __dict__:', dict_proxy({'a': 0, '__dict__': <attribute '__dict__' of 'TestDict' objects>, '__module__': '__main__', 'b': 1, 'static_test': <staticmethod object at 0x10f0f9360>, 'test': <function test at 0x10f0fe758>, '__weakref__': <attribute '__weakref__' of 'TestDict' objects>, 'class_test': <classmethod object at 0x10f0f9328>, '__init__': <function __init__ at 0x10f0fe6e0>, '__doc__': None}))
类dict里存放类的静态函数、类函数、普通函数、全局变量以及一些内置的属性
- 类对象的
__dict__
('class obj __dict__:', {'a': 2, 'b': 3})
类对象的__dict__存放类的属性:self.xxx
继承关系中的__dict__
# -*- coding: utf-8 -*-
class Parent(object):
a = 0
b = 1
def __init__(self):
self.a = 2
self.b = 3
def parent_test(self):
pass
class Child(Parent):
a = 4
b = 5
def __init__(self):
super(Child, self).__init__()
self.b = 7
self.c = 8
def child_test(self):
pass
if __name__ == '__main__':
parent_obj = Parent()
child_obj = Child()
print('Parent __dict__:', Parent.__dict__)
print('Child __dict__:', Child.__dict__)
print('Parent obj __dict__:', parent_obj.__dict__)
print('Child obj __dict__:', child_obj.__dict__)
输出
('Parent __dict__:', dict_proxy({'a': 0, '__module__': '__main__', 'b': 1, 'parent_test': <function parent_test at 0x10c5e12a8>, '__dict__': <attribute '__dict__' of 'Parent' objects>, '__weakref__': <attribute '__weakref__' of 'Parent' objects>, '__doc__': None, '__init__': <function __init__ at 0x10c5e10c8>}))
('Child __dict__:', dict_proxy({'a': 4, '__module__': '__main__', 'b': 5, '__doc__': None, '__init__': <function __init__ at 0x10c6bdd70>, 'child_test': <function child_test at 0x10c6bdde8>}))
('Parent obj __dict__:', {'a': 2, 'b': 3})
('Child obj __dict__:', {'a': 2, 'c': 8, 'b': 7})
可以看出
- 继承关系，父类的
__dict__并不会影响子类的__dict__因为 - 子类
__init__初始化了父类的__init__, 才会将父类对象的属性加到子类对象的__dict__
def __init__(self):
super(Child, self).__init__()
应用
python中，用__dict__可以达到一些简化代码的目的
- 简单例子：
class Person:
def __init__(self,_obj):
self.name = _obj['name']
self.age = _obj['age']
self.energy = _obj['energy']
self.gender = _obj['gender']
self.email = _obj['email']
self.phone = _obj['phone']
self.country = _obj['country']
是不是很繁琐？用dict一句话就可以搞定
class Person:
def __init__(self,_obj):
self.__dict__.update(_obj)
- 复杂例子
在适配器模式中，
class Synthesizer:
def __init__(self, name):
self.name = name
def __str__(self):
return 'the {} synthesizer'.format(self.name)
def play(self):
return 'is playing an electronic song'
class Human:
def __init__(self, name):
self.name = name
def __str__(self):
return '{} the human'.format(self.name)
def speak(self):
return 'says hello'
class Computer:
def __init__(self, name):
self.name = name
def __str__(self):
return 'the {} computer'.format(self.name)
def execute(self):
return 'executes a program'
class Adapter:
def __init__(self, obj, adapted_methods):
self.obj = obj
self.__dict__.update(adapted_methods)
print ("self.__dict__:", self.__dict__)
def __str__(self):
return str(self.obj)
def main():
objects = [Computer('Asus')]
synth = Synthesizer('moog')
objects.append(Adapter(synth, dict(execute=synth.play)))
human = Human('Bob')
objects.append(Adapter(human, dict(execute=human.speak)))
for i in objects:
print('{} {}'.format(str(i), i.execute()))
类Adapter中self.__dict__.update(adapted_methods)，其实相当于
class Adapter:
def __init__(self, obj, adapted_methods):
self.obj = obj
self.execute = adapted_methods
def main():
objects.append(Adapter(synth, synth.play))
打印结果可以看出来
('self.__dict__:', {'execute': <bound method Synthesizer.play of <__main__.Synthesizer instance at 0x027B1CB0>>, 'obj': <__main__.Synthesizer instance at 0x027B1CB0>})
